Bleed brakes after 5 months - MVAgusta.net
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post #1 of 20 (permalink) Old 12-01-2018, 09:31 AM Thread Starter
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Bleed brakes after 5 months

Hi,
about 5 months ago I did, on my F3 675 (2016), the brakes bleeding (rear and front), now after more or less 2000km the rear brake pedal goes down and so I think that it's necessary another brake bleeding.
I think that this isn't normal after 2000km/5 months.

What do you think?
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post #2 of 20 (permalink) Old 12-01-2018, 09:40 AM
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Its Italian. Ofcourse its normal.

Jokes aside, I asked my mechanic at the dealership what the problem is with these weak rear brakes. Its common and even when bled they dont work properly anyways.
As long as you can feel that rear brake is actualling braking I think you're fine.

My rear brake got dark pretty fast. So im up for a fresh brake fluid aswell. My front fluids are still nice and gold after 2 years.

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post #3 of 20 (permalink) Old 12-01-2018, 09:50 AM
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I think the proximity of the rear master cylinder to the exhaust heat tends to degrade the fluid quickly. Use a high quality brake fluid (yes, there are differences).

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post #4 of 20 (permalink) Old 12-01-2018, 09:58 AM Thread Starter
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I have doubts also because braking pushing the rear brake pedal the stop led light doesn't work.
This, together problem described before, could be a signal of a rear brake pump malfunction?
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post #5 of 20 (permalink) Old 12-01-2018, 01:44 PM
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@.fabioss.
When I encounter problems like this, you have to get the system back to zero-zero - like it was when it was new. You have two problems as I understand it - rear brake does not work effectively and the brake light does not illuminate via the rear brake. You are now most likely beyond a mere brake bleed to fix this. You've bled the brake and it still does not work. First, check for leaks and they may not be that obvious - look for "breaths" of fluid or dirt around the sealing washers. Assuming that there are no obvious leaks, the next thing to check are the seals in the master cylinder. You will have to take the piston out to do this but most of the systems are pretty simple - it could be something as simple as a seal installed backwards, which is not unheard of. Next, check the seals in the brake caliper. Replace any seals that have the slightest of imperfections and also analyze why they got them. The surfaces of the pistons in the master cylinder and caliper should also be carefully checked for scoring. In all this, dirt and water are the enemies - make sure everything is clean. If the rear caliper is upside down on the rear disc, remove it and bleed the caliper with the nipple upright. On many systems, you will leave air in the system by attempting to bleed a brake with the nipple underneath.

Re the brake light, first understand how the system turns the light on. Either it is an electrical micro switch or a hydraulic pressure switch. Test the micro switch off the bike using a multimeter or a separate power source and a light bulb. Also check the light bulb and its holder to see if you can illuminate the light by unplugging the wire harness and putting current in it to the brake light. Also make sure the bulb is correct and correctly installed in the holder. The hydraulic pressure switch is more difficult to test so, if everything else works, I would then replace it.
Hope this helps
Rob
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post #6 of 20 (permalink) Old 12-01-2018, 02:34 PM Thread Starter
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Thanks for help. I will bring the F3 to my mechanic and we will try to understand how solve the problem.
However, if the problem regards the rear brake pump (cod. 800089313) it costs more or less 100€.

Last edited by .fabioss.; 12-01-2018 at 02:36 PM.
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post #7 of 20 (permalink) Old 12-01-2018, 04:29 PM Thread Starter
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During the fixing of this problem I think that I will do a complete brakes bleeding (rear and front) for better result.
What's the better brake fluid that I can buy?
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post #8 of 20 (permalink) Old 12-02-2018, 01:13 AM
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Quote:
Originally Posted by .fabioss. View Post
Thanks for help. I will bring the F3 to my mechanic and we will try to understand how solve the problem.
However, if the problem regards the rear brake pump (cod. 800089313) it costs more or less 100€.
Don't start throwing parts and money at it just yet until you have zeroed the system as noted....These systems are inherently simple. If they weren't, everyone would be crashing into each other.

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post #9 of 20 (permalink) Old 12-02-2018, 01:25 AM
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Can I say one more thing?
The rear brakes on Italian sport bikes - at least the more modern ones - are fairly weak and are so for a purpose. First of all, 95% of the stopping power is in the front and so the rear is viewed as being secondary. Second, an old time and reputable Ducati mechanic told me that the rears are weak to prevent rear wheel lock up under heavy braking up front. As the weight transfers to the front, less is available to act against the rear wheel and therefore brake. So a powerful rear brake would make you lock up the rear fairly easily and could cause a high side crash. While I agree with you in insisting that all the systems should work on the bike as intended, the rear brake should only be used for modulating and fine tuning corner speeds under braking (also known as trail braking) and not really for out and out stopping. Get the thing to work as good as it possibly can and then move on!
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post #10 of 20 (permalink) Old 12-02-2018, 03:21 AM
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I only use my rear as a handbrake pulling off from inclines. Coming from dirtbikes where I used the rear for everything, this MV has done an excellent job of making me forget that a rear brake ever existed. I only use front now on both track days and road and happy with it.

Mine doesnt have ABS and it is very easy to lock up the rear (after its properly bled and works for a few days), to the point where I feel its not worth the risk for that extra 5-10% braking power.

If yours has an ABS, there is a special way of bleeding the brakes. Think there are a few videos on youtube regarding the MV bleeding procedure. There may be a service bulletin too.
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